The present invention relates to a method of manufacturing a sewer waste-water treating agent by utilizing as material the waste silica-alumina catalyst (or F.C.C. catalyst) discarded after serving as the catalyst for the fluid-bed type cracking of petroleum, and it is intended to provide a sewer waste-water treating agent which is not only effective for removing ammoniacal nitrogen and heavy metal ions contained in sewer waste-water but also convenient for solid-liquid separation.
The sewer waste-water generally contains varieties of harmful substances, and these substances would give rise to various troubles in daily life. For instance, ammoniacal nitrogen, phosphate and the like are said to cause an extraordinary growth of microbes in lakes and marshes, rivers and the sea as they constitute a source of nutrition for microbes in water. Also, it is a well known fact that the ions of heavy metal, such as cadmium, lead, copper, etc. have a very bad influence upon the human body. From this point of view, the treatment of sewer waste-water aimed at the removal of the above-mentioned harmful substances is considered indispensable, and accordingly, various studies are under way. The treatment of sewer waste-water for this purpose has ordinarily been conducted by applying the active sludge process, the active carbon process and the like, but, according to these processes, ammoniacal nitrogen can not be removed satisfactorily. Therefore, for the purpose of removing ammoniacal nitrogen, such processes as oxidation by utilizing microbes or airstripping have been employed, but these processes are all defective in that the process per se is intricate and costly. As to the removal of heavy metals contained in sewer waste-water, in addition to the ion-exchange process employing ion-exchange resin, the process of treating with chemicals, the process of treating with active carbon, etc. have been applied, but these processes are not very practical inasmuch as they are too expensive in respect of the cost of the required apparatus and/or the cost of operation thereof.
On the other hand, there has also been tried a process of removing ammoniacal nitrogen and/or heavy metal ions by utilizing zeolite or a natural silicate such as clay minerals. This process seems to utilize the cation-exchange property inherent in the natural zeolite or clay minerals, and indeed it is effective for removing ammoniacal nitrogen and/or heavy metal ions. However, this process is defective in that, inasmuch as the natural zeolite and other clay minerals, when brought in contact with water, are apt to give rise to disintegration of grains to turn into very fine particles, rendering it difficult to perform solid-liquid separation, and therefore a special care must be taken in practicing this process industrially.
By the way, the amount of consumption of silica-alumina catalyst has shown a yearly increase with the recent growth of petroleum industry, and at present it is consumed in an amount of as much as about 100,000 tons a year. This means that the same amount of waste catalyst has been discharged annually, while as for the means of disposal of this enormous volume of waste catalyst, the method of burying it in the ground has so far been exclusively adopted. However, a waste catalyst of this kind is composed essentially of ingredients similar to zeolite and is in the form of a firm sinter as a result of repeated exposure to high temperatures within the cracking apparatus. Therefore, subject to imparting cation-exchange property similar to that of the above-mentioned natural zeolite by treating said waste catalyst in some way or other, not only an effective utilization of waste catalyst is feasible but also there can be produced a sewer waste-water treating agent useful for the removal of ammoniacal nitrogen and/or heavy metal ions and free of disintegration even when brought in contact with water.